It is disclosed in the art to determine in motor vehicles the tire pressure or a quantity representative of the tire pressure by means of pressure measuring systems (TPMS=Tire Pressure Measuring System) based on a pressure sensor or, without using pressure sensors, by means of systems based on the wheel speed (DDS=Deflation Detecting System).
In the so-called TPMS system, the measured pressure along with the temperature is sensed by means of sensors arranged in the tire and transmitted in a wireless manner to a receiver installed in the vehicle. The pressure data is evaluated and the pressure prevailing in the individual tires is determined in a control device.
For the conventionally used safety and motor vehicle control systems such as ABS, TCS, ESP, DDS, etc., a relatively exact knowledge of the rotational behavior of the individual vehicle wheels is necessary. Nowadays, vehicles are therefore equipped with passive or active wheel speed sensors, which supply the required input signals for the various safety and control systems. Thus, the tire pressure that cannot be derived directly from the wheel speeds is determined indirectly by way of the dynamic rolling circumference of the individual vehicle wheel e.g. by means of the DDS system (Deflation Detecting System). The load dependency of the dynamic rolling circumference rather must be considered a disturbance variable in pressure loss detection by means of DDS.
A method for measuring the load exerted on the tire which is determined, among others, by the actual tire pressure and the wheel load or wheel load distribution during operation of the vehicle, meaning during driving, has not been known so far. It is not sufficient to monitor the tire pressure loss because the charge or load exerted on the tire, to a larger extent than the tire pressure, is responsible for the safety and durability of the tire and because different tire pressures are required for a comfortable driving behavior and ideal charge exerted on the tire depending on the wheel load or wheel load distribution.